UFOZoo

Cron Generator — Build Linux Crontab Schedule Online

Build, validate, and understand cron schedules visually. Features field selectors, quick presets, human-readable descriptions, and next execution preview.

Features

  • ✓Visual cron expression builder with intuitive dropdown selectors for each field (minute, hour, day, month, weekday)
  • ✓Quick presets for common schedules: every minute, hourly, daily, weekly, monthly, and business hours
  • ✓Real-time human-readable description translation — converts * * * * * to 'Every minute' instantly
  • ✓Next 5 execution times preview with exact dates and times in your local timezone
  • ✓Bidirectional editing — modify the expression directly or use the visual builder, changes sync both ways
  • ✓Built-in validation with clear error messages for invalid cron syntax
  • ✓Supports standard 5-field Linux crontab format (minute hour day month weekday)
  • ✓Copy-to-clipboard functionality for generated expressions with one click
  • ✓100% browser-based — no server processing, your cron data never leaves your device

How to Use

  1. 1Select a quick preset from the top row (Every Minute, Hourly, Daily, etc.) or configure each field manually.
  2. 2For manual configuration, use the dropdowns: Minute (0-59), Hour (0-23), Day (1-31), Month (1-12), Weekday (0-6).
  3. 3Use * for 'every value', */n for intervals (e.g., */15 = every 15 min), and commas for lists (e.g., 1,15).
  4. 4Read the human-readable description below the expression to verify your schedule is correct.
  5. 5Check the 'Next Executions' section to see when the job will run next.
  6. 6Click the copy button to copy the expression to your clipboard for use in crontab or applications.
  7. 7Use the Next 5 Executions section to preview exactly when your cron job will run. This helps you verify your expression by showing actual dates and times in your local timezone before deploying to production.
  8. 8Switch between different presets to learn how common cron patterns work. Each preset automatically fills all fields and shows the corresponding next execution times, making it easy to understand the relationship between the expression and the actual schedule.

Frequently Asked Questions

What is a cron expression?

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A cron expression is a string of 5 fields separated by spaces that defines when a scheduled task should run. The fields are: minute (0-59), hour (0-23), day of month (1-31), month (1-12), and day of week (0-6, where 0 is Sunday). For example, '0 9 * * 1' means 'at 9:00 AM every Monday'.

What's the difference between * and */n?

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The asterisk (*) means 'every possible value' for that field. */n means 'every n-th value'. For example, * in the minute field means every minute, while */15 means every 15 minutes (at 0, 15, 30, 45). Similarly, */2 in the hour field means every 2 hours.

How do I schedule a job for business hours only?

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Use '0 9-17 * * 1-5' for 9 AM to 5 PM on weekdays. The '9-17' specifies hours 9 through 17 (5 PM), and '1-5' specifies Monday (1) through Friday (5). For specific times like 9 AM and 3 PM, use commas: '0 9,15 * * 1-5'.

Why does my cron expression show an error?

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Common errors include: values out of range (e.g., minute > 59), invalid characters, or missing fields. Each field has specific valid ranges: Minute (0-59), Hour (0-23), Day (1-31), Month (1-12), Weekday (0-6). The tool validates your expression in real-time and shows clear error messages.

Can I use this for AWS EventBridge or Quartz Scheduler?

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This tool generates standard 5-field Linux crontab expressions. AWS EventBridge uses a 6-field format with an additional 'seconds' field at the beginning. Quartz Scheduler supports extended syntax like L (last), W (weekday), and # (nth occurrence) which are not supported by standard cron. For these systems, you may need to adjust the generated expression.

How do I set up a cron job on Linux?

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Use the 'crontab -e' command to edit your cron jobs. Add a line with your expression followed by the command to run, like: '0 3 * * * /path/to/backup.sh'. Save and exit — cron will automatically pick up the changes. Use 'crontab -l' to list your current jobs.

How do I schedule a backup at 2:30 AM every Sunday?

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Use '30 2 * * 0'. The '30' is the minute, '2' is the hour (2 AM), '*' means every day of month, '*' means every month, and '0' means Sunday (0=Sunday, 6=Saturday). For every Sunday at 2:30 AM, this expression triggers weekly backups reliably without interfering with weekday operations.

What is the difference between cron and systemd timers?

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Cron is the traditional Linux job scheduler using crontab files with 5-field expressions. Systemd timers are the modern alternative with more features like persistent timers (run missed tasks after boot), calendar-based scheduling, randomized delays, and better logging. Systemd timers use a different syntax (OnCalendar=). This tool generates standard cron format, not systemd timer syntax.

Can I schedule a job for the last day of every month?

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Standard cron does not support 'last day of month' directly. A common workaround is to schedule '0 6 28-31 * *' and add a check inside the script to verify whether today is the last day before executing. Some cron implementations support L in the day field, but this is not standard. For precise last-day scheduling, consider using a script-level date check.

What are common cron use cases?

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Common cron use cases include: system maintenance (log rotation at midnight), database backups (daily at 3 AM), report generation (weekly on Monday morning), email newsletters (daily at 10 AM), cache clearing (every 6 hours), monitoring checks (every 5 minutes), data synchronization (hourly), and certificate renewal (monthly). Choose schedules that minimize load during peak traffic hours.

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